The goal is to acquire a solid background in microbial and molecular genetics. The educational program will be carried out in the laboratory of Dr. Frederick Ausubel in the Department of Molecular Biology at the Massachusetts General Hospital, and will focus on characterization of the molecular genetic mechanisms in E. coli involved in adaptation to oxidant stress. The construction and characterization of a strain of E. coli carrying deletion for the manganese-superoxide dismutase gene (sodA), will be of initial interest. Laboratory work will be complemented by courses given in the MIT Graduate Biology Program, and by seminars at MGH, MIT and HMS. Phase II will take place under the guidance of Dr. Allan Walker, Chief of Pediatric Gastroenterology and Nutrition at MGH and CHMC, who has had a long term interest in studying the mammalian gut as an organ of host defense. Here, expertise gained in bacterial genetic manipulation during phase I will be used to develop a molecular genetic approach to the study of host/microbe interaction.